We propose to correlate the structure and function of taste cells in the mouse and mudpuppy (Necturus maculosus). In particular, we will test the hypothesis that calcium entry during chemical stimulation evokes transmitter release and excites gustatory nerve terminals in the taste bud. Our techniques for studying this problem are light and electron microscopy, high voltage electron microscopy, scanning electron microscopy, and intracellular microelectrode recording. To characterize the complex cellular interrelationships among taste cells, we will section vallate, foliate, and fungiform taste buds serially in thin and thick (0.5-1 micron) sections for transmission and high voltage electron microscopy. This, along with computer-assisted analysis, will allow us to reconstruct taste buds, cells, and synapses in three dimensions. We have developed new protocols for EM fixation which allow us to resolve ultrastructural features, including synaptic foci in great detail. Furthermore, we have devised new methods for impaling single taste cells with glass microelectrodes and which have allowed us to obtain very stable intracellular recordings. We now proposed to use these techniques to examine whether, and to what extent, calcium is involved in chemosensory transduction mechanisms.